1. FIELD OF THE INVENTION
This invention concerns preparation of urethane-type polymers and more particularly the preparation of urethane-type polymers by the condensation-rearrangement of cyclic nitrile carbonates and oxalates with organic nucleophilic compounds.
2. PRIOR ART
U.S. Pat. No. 3,531,425 describes the preparation of a novel class of urethane-type polymers obtained by condensing various nitrile carbonates, sulfites or oxalates with nucleophilic compounds such as polyols, polythiols, and polyamines. This condensing-rearrangement reaction may be used to produce elastomers, films and foams depending upon the nature of the reactants and the particular conditions under which the reaction is carried out. U.S. Pat. No. 3,652,507 describes the preparation of high molecular weight polymers by the same type reaction, the high molecular weight products being obtained by the use of specific catalysts. Co-pending U.S. Patent Application Ser. No. 182,529, filed Sept. 21, 1971 discloses a method of preparing polyurethane-type foams by the above reaction, again with the use of specific catalysts now U.S. Pat. No. 3,746,667. U.S. Pat. No. 3,256,213 discloses a method of preparing cellular polyurethane-type polymers by reacting isocyanates with polyamino compounds, the innovative feature being the reduction of the reactivity of the polyamino compound by reaction with carbon dioxide to permit thorough mixing of the reactants before reaction takes place. The polyamino compound is reactivated by reaction with a metallic oxide. The disclosures of the above patents and application are incorporated herein by reference.
The above-described method of preparation of polyurethane-type polymers by the condensation-rearrangement of cyclic nitrile compounds with organic nucleophilic compounds is somewhat complicated by the fact that upon reaction of the cyclic nitriles and nucleophilic compounds one mole of a gas, sulfur dioxide, carbon monoxide or carbon dioxide (a mole each of carbon monoxide and carbon dioxide when cyclic nitrile oxalates are used) is produced for each condensation of a cyclic nitrile group and a nucleophilic group. Thus, if it is desired to produce a thermoplastic polymer, such as a fiber or a film, it is necessary to carry out the reaction under carefully controlled conditions to allow the released gas to escape without affecting the integrity of the fiber or film. Furthermore, when foams are prepared by the above-described process, the density of the foam is more or less determined by the amount of released gas that is available for foaming purposes. The density of the foam could be reduced by the use of additional blowing agents but it is difficult to produce foams of greater density than would naturally occur by the release of the fixed amount of gas formed by the condensation-rearrangement of the reactants. Thus, to produce foams of density greater than would be automatically produced by the stoichiometric amount of gas released, the reaction must be carried out under specific conditions or the reactants must be carefully selected to produce a given amount of released gas per unit weight of product. These restrictions are cumbersome and it is sometimes difficult to produce a product having the desired properties.
A method has now been discovered which eliminates the above difficulties when a cyclic nitrile compound is used which, upon reaction, produces carbon dioxide. This newly discovered method makes it possible to produce polyurethane-type elastomers and films by the condensation-rearrangement reaction between cyclic nitrile compounds and organic nucleophilic compounds without concern over the amount or rate of release of carbon dioxide from the forming product. Furthermore, it is possible, by virtue of this invention, to produce, without difficulty, polyurethane-type foam materials of high density.
Accordingly, it is an object of the invention to present an improved process for the preparation of urethane-type polymers by the condensation-rearrangement reaction between carbon dioxide-producing cyclic nitrile compounds and nucleophilic compounds.
It is a second object to present an improved process for the preparation of high density foamed urethane-type polymers by the reaction of carbon-dioxide producing cyclic nitrile compounds and nucleophilic compounds.
It is a third method of the invention to present novel high density urethane-type polymers.
It is a fourth object of the invention to present a method of eliminating or controlling the amount of free carbon dioxide in products being formed by the reaction of cyclic nitrile carbonates and/or oxalates and organic nucleophilic compounds.
These and other objects will become more apparent from the following description and examples.
According to the invention, urethane-type polymers are prepared by the reaction of carbon dioxide-producing cyclic nitrile compounds with organic nucleophilic compounds in the presence of calcium oxide, barium oxide or mixtures of these. The preferred carbon dioxide-producing compounds are the cyclic nitrile carbonates. The calcium and/or barium oxide may be present in an amount to consume all or any portion of the carbon dioxide produced in the condensation-rearrangement reaction.